Hi Scott,
I understand the inconvenience caused by this issue.
Firstly, I'd like to confirm the following things:
1. Only the "company" account encounters this issue in the organization.
2. You can login to Office 365 OWA by using this account.
3. The Outlook for Mac cannot connect to the Exchange Online and returned the error message with logon failure.
4. You have checked and repaired Keychains by using "Keychain First Aid". If you haven't used "Keychain First Aid", please go to "Keychain Access" > "Keychain First Aid".
If I have misunderstood anything, please feel free to let me know.
Also, please try the steps below to troubleshoot this issue:
1. Update Office for Mac to the latest version.
2. Set up the Office 365 account on another MacBook. Will this issue occur?
Thanks,
Edward Qu